Spinal Level Reflexes

Question 1

Characteristics of Spinal level reflexes?

Answer 1

1. Involuntary responses to stimuli
2. Monosynaptic or polysynaptic (involve interneurons)
3. Basis for unconscious motor function and basic defense mechanisms

Question 2

What is the stimulus for Stretch (myotactic) Reflexes?

Answer 2

Muscle stretch

Question 3

What is the function of Myotatic Reflexes?

Answer 3

Functions for Maintenance of (1) muscle tone (2) support agonist muscle contraction and (3) provide feedback about muscle length

Question 4

Describe the reflex arc for myotatic reflexes.

Answer 4

Afferent (away from brain) Ia fiber from muscle spindle to alpha motor neurons projecting back to muscles of origin (monosynaptic)

Question 5

Who is the stretch reflex clinically tested?

Answer 5

Apply stretch to deep tendons

Question 6

Describe Reciprocal inhibition

Answer 6

Via an inhibitory interneuron. The same stretch stimulus inhibits the ANTAGONIST muscle

Question 7

Reciprocal innervation describes what?

Answer 7

Describes the effect of a stretch stimulus on agonist (autogenic facilitation), antagonist (reciprocal inhibition), and synergistic muscles (facilitation)

Question 8

What is the stimulus for Inverse Stretch (Myotatic) Reflex?

Answer 8

Muscle contraction

Question 9

What is the Reflex arc for inverse stretch reflex?

Answer 9

Multiple sensory receptors and corresponding fiber types activate inhibitory interneuron to muscle of origin (polysynaptic)

Question 10

What is the function of the inverse stretch reflex?

Answer 10

Provide agonist inhibition, diminution of force of agonist contraction, stretch-protection reflex

Question 11

True or false: the stretch reflex forms part of the gamma reflex loop

Answer 11

True

Question 12

What does the gamma reflex loop allow?

Answer 12

Allows muscle tension to come under control of descending pathways (reticulospinal, vestibulospinal, and others)

Question 13

True or false: descending pathways excite gamma motor neurons, causing contraction of muscle spindle, and in turn increased stretch sensitivity and increased rate of firing form spindle afferents; impulse are then conveyed to alpha motor neurons

Answer 13

True

Question 14

What is the stimulus for the Flexor (withdrawal) reflex?

Answer 14

Cutaneous sensory stimuli

Question 15

What is the function of the flexor (withdrawal reflex)?

Answer 15

Functions as protective withdrawal mechanism to remove body part from harmful stimuli

Question 16

What is the stimulus of crossed extension reflex?

Answer 16

Noxious stimuli and reciprocal action of antagonists

Flexors are excited causing extension on same side to inhibited; opposite occurs on contralateral leg